Oscillatory wave motor

ABSTRACT

An oscillatory wave motor includes an oscillator having an oscillation body and an electro-mechanical energy-converting element, and a flexible heat-conducting member configured to dissipate heat generated by the oscillatory wave motor. The oscillatory wave motor drives a moving body in contact with a contact portion formed in the oscillation body by an elliptical movement of the oscillator, and the heat-conducting member is provided in addition to a heat-conducting path that conducts heat generated by the oscillatory wave motor through an oscillator supporting member that supports the oscillator or a heat-conducting path that conducts heat through the moving body.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to oscillatory wave motors.

2. Description of the Related Art

In recent years, oscillatory wave motors have been commercially used as,for example, motors for driving auto-focus lenses of single-lens reflexcameras, because of their low-speed and large-torque characteristics.Such oscillatory wave motors are required to have a smaller size and alarger output.

In order to reduce the size while increasing the output, measures mustbe taken against heat generation and temperature rise of oscillatorywave motors.

That is, the energy loss, which is the energy inputted into anoscillatory wave motor but not outputted therefrom, is converted intothermal energy.

Therefore, if an oscillatory wave motor is reduced in size whileincreased in output, the energy loss per unit volume and the energy lossper unit surface area increase, causing temperature rise.

Such temperature rise degrades the function of components of theoscillatory wave motor and affects the performance of the oscillatorywave motor. Accordingly, measures must be taken against such a problem.

To counter this problem, Japanese Patent Laid-Open No. 3-253270 proposesan oscillatory wave motor having an increased heat dissipationefficiency, as shown in FIG. 4.

As shown in FIG. 4, this oscillatory wave motor is configured such thata piezoelectric element 104 is bonded to one side of a ring-likemetallic elastic member 103 and such that alternating voltages havingdifferent phases are applied to two driving piezoelectric element groupsformed on the piezoelectric element 104.

By applying the alternating voltages, two standing waves are excited onthe elastic member 103. By combining these standing waves, a travelingwave, which is a bending vibration, is formed. A ring-like moving-bodymain ring portion 106, to which an abrasion-resistant member 107 isbonded, is pressed against the other side of the elastic member 103 bymeans of a pressure spring 110. The moving-body main ring portion 106and the abrasion-resistant member 107 constitute a moving body 108. Themoving body 108 and an output shaft 111 are rotated by the frictiondrive produced by the traveling wave formed on the elastic member 103.

Meanwhile, the above-described Japanese Patent Laid-Open No. 3-253270takes the following measures to counter heat generation and temperaturerise of the oscillatory wave motor. The frictional heat generatedbetween the moving body 108 and an oscillator 105, which is composed ofthe elastic member 103 and the piezoelectric element 104, as well as theheat generated in the oscillator 105, heats the oscillator 105.

The heat is conducted from an inside-diameter portion of the oscillator105, which is in contact with a base 102, through a heat-conductingmember 116 to a cover 101 and is quickly dissipated by a fan 117.

However, this configuration requires a separately provided heatdissipating member, such as a fan, which increases the component count,making a reduction in size difficult.

Furthermore, in this configuration, the heat-conducting member 116inhibits oscillation of the oscillator 105 and degrades the performance.

A configuration in which heat is dissipated outside without providingthe fan 117 or the heat-conducting member 116, but by means of heatconduction of other members, causes the following problems. The heatgenerated by the friction between the elastic member 103 and the movingbody 108, the heat generated in the piezoelectric element 104, the heatgenerated at the bonding surface between the elastic member 103 and thepiezoelectric element 104, and the heat generated in the elastic member103, at a portion near the piezoelectric element 104, are dissipated byheat conduction through an elastic-member thin portion 103-b serving asan oscillator supporting member.

Alternatively, the heat is dissipated from the moving body 108 side, byheat conduction through a rubber ring 109 serving as a damper, apressure spring 110 serving as a pressure-applying member, and an outputshaft 111.

However, the elastic-member thin portion 103-b, serving as theoscillator supporting member, has a small thickness so as not to inhibitoscillation of the oscillator 105, and thus, has a small cross-sectionalarea. This is not suitable for heat conduction.

Furthermore, the rubber ring 109 serving as a damper is made of a lowheat-conducting material, and the pressure spring 110 has a smallthickness so as to reduce the spring constant to ensure the precision ofpressure setting. This also inhibits heat conduction.

In addition, components of the oscillatory wave motor are fastened withscrews and the like, and thus, heat is conducted between differentcomponents through the contact surfaces therebetween. Thus, the thermalcontact resistance prevents heat conduction.

As has been described above, conventional oscillatory wave motors cannotsufficiently dissipate heat. Thus, temperature rise of oscillatory wavemotors degrades the function of the components thereof and degrades themotor performance.

The present invention has been made in view of the above-describedproblems, and it provides an oscillatory wave motor capable ofpreventing degradation of performance due to temperature rise andreducing the size while increasing the output.

SUMMARY OF THE INVENTION

An oscillatory wave motor of the present invention includes anoscillator having an oscillation body and an electro-mechanicalenergy-converting element, and a flexible heat-conducting memberconfigured to dissipate heat generated by the oscillatory wave motor.The oscillatory wave motor drives a moving body in contact with acontact portion formed in the oscillation body by an elliptical movementof the oscillator, and the heat-conducting member is provided inaddition to a heat-conducting path that conducts heat generated by theoscillatory wave motor through an oscillator supporting member thatsupports the oscillator or a heat-conducting path that conducts heatthrough the moving body.

The present invention can provide an oscillatory wave motor capable ofpreventing degradation of performance due to temperature rise andreducing the size while increasing the output.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an oscillatory wave motor accordingto a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of an oscillatory wave motor accordingto a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of an oscillatory wave motor accordingto a third embodiment of the present invention.

FIG. 4 is a cross-sectional view of an oscillatory wave motor disclosedin Japanese Patent Laid-Open No. 3-253270.

DESCRIPTION OF THE EMBODIMENTS

An example of the configuration of an oscillatory wave motor accordingto embodiments of the present invention will be described, whichincludes an oscillator having an oscillation body and anelectro-mechanical energy-converting element. Elliptical movement of theoscillator drives a moving body in contact with a contact portion formedon the oscillation body.

First Embodiment

Referring to FIG. 1, an example of the configuration of an oscillatorywave motor according to a first embodiment of the present invention willbe described.

FIG. 1 shows a piezoelectric element 1 composed of an electro-mechanicalenergy-converting element, a metallic elastic member (oscillation body)2, and an oscillator 3 composed of the elastic member 2 and thepiezoelectric element 1 attached to one side of the elastic member 2.

FIG. 1 also shows a moving-body contact spring portion 4, a moving-bodyunwanted-oscillation damper 5 composed of an elasticoscillation-attenuating material, such as rubber, for attenuatingunwanted vibrations of a moving body 7, and a moving-body main ringportion 6.

The moving-body contact spring portion 4, the moving-bodyunwanted-oscillation damper 5, and the moving-body main ring portion 6constitute the moving body 7.

FIG. 1 also shows an oscillation-propagation blocking damper 8 composedof an elastic oscillation-attenuating material, such as rubber, forblocking propagation of the oscillation of the moving body 7.

FIG. 1 also shows a disc spring 9 serving as a pressure-applying member,a disc-spring fixing member 10, an output shaft 11, a bearing 12, aplain bearing 13, a base 14, and a cover 15.

The driving principle of the motor is basically the same as theconventional one. The moving body 7 is rotated by the traveling waveexcited by the oscillator 3.

The moving-body contact spring portion 4 follows the oscillation of theoscillator 3 to prevent noise and ensure stable rotation.

The disc spring 9 is fixed to the disc-spring fixing member 10 fitted tothe output shaft 11 and presses the moving body 7 against the oscillator3 with the oscillation-propagation blocking damper 8 therebetween.

The oscillation-propagation blocking damper 8 restrains the moving body7 and the disc spring 9 in the rotation direction by means of africtional force. Accordingly, when the moving body 7 is rotated, therotational force is transmitted to the output shaft 11 through theoscillation-propagation blocking damper 8, the disc spring 9, and thedisc-spring fixing member 10.

Furthermore, the oscillation-propagation blocking damper 8 serves toprevent minor oscillations of the moving body 7, caused by theoscillation of the oscillator 3, from being propagated to the discspring 9 and to make the pressure of the disc spring 9 applied to themoving body 7 uniform.

The moving-body unwanted-oscillation damper 5 attenuates unwantedvibrations of the moving-body contact spring portion 4 caused by theoscillation of the oscillator 3.

The output shaft 11 is supported by the bearing 12 and the plain bearing13, which are held by the base 14, so as to be freely rotated.

The oscillator 3 is fixed by caulking an oscillator inside-diameterportion 3-a to the base 14 or by fastening them with screws.

Furthermore, the motor is entirely covered by the cover 15 fixed to thebase 14.

Heat-conducting members 16, 17, 18, and 19 are flexible and have theshapes of thin-plates, i.e., strips. The heat-conducting member 16 isjoined to the base 14 and the oscillator 3, the heat-conducting member17 is joined to the moving-body contact spring portion 4 and themoving-body main ring portion 6, the heat-conducting member 18 is joinedto the moving-body main ring portion 6 and the disc spring 9, and theheat-conducting member 19 is joined to the disc spring 9 and the outputshaft 11.

The heat-conducting members 16 to 19 are disposed such that they are incontact with the members to which they are joined with large contactareas, so as to increase the heat conductivity therebetween. Theheat-conducting members 16 to 19 are bonded by adhesion, brazing, orwelding.

Although the heat-conducting members 16 to 19 are made of thin copperplates, they are not limited thereto. The heat-conducting members 16 to19 may be made of a material having high heat conductivity, such asaluminum, graphite, or carbon fiber; or a material containing theaforementioned material.

Furthermore, the heat-conducting members 16 to 19 are not limited tothin plate shaped. As long as the heat-conducting members 16 to 19 donot inhibit oscillation of the members to which they are joined,multiple string-like members, such as wires, may be provided.

A large portion of the internal frictional heat generated in theoscillator 3 is produced at the piezoelectric element 1 and an outsidediameter portion 3-b of the oscillator 3, where the joint surfacebetween the piezoelectric element 1 and the elastic member 2 is located.

Furthermore, frictional heat is generated at the frictional drivingsurface between the oscillator 3 and the moving body 7.

The heat generated by the oscillatory wave motor is conducted to thebase 14 not only through an oscillator supporting member 3-c and afastening surface 20 between the oscillator 3 and the base 14, but alsothrough the heat-conducting member 16.

Because a typical oscillator supporting member has a small thickness ora thin, pin-like shape so as not to inhibit oscillation of theoscillator, the oscillator supporting member 3-c has a small thicknessand. Thus, the heat conductivity thereof is not high.

Furthermore, the fastening surface 20 between the oscillator 3 and thebase 14 serves as a thermal resistor.

However, because the heat conduction through the heat-conducting member16 contributes to heat dissipation, it is possible to preventtemperature rise of the oscillator 3 and moving body 7, as well as toprevent degradation of the motor performance due to the temperaturerise.

Furthermore, because the heat-conducting member 16 is flexible, it doesnot inhibit oscillation of the oscillator 3. Thus, the motor performanceis not degraded.

The heat generated by the oscillatory wave motor is also dissipatedoutside by the heat conduction through the moving body 7, theoscillation-propagation blocking damper 8, the disc spring 9, thedisc-spring fixing member 10, and the output shaft 11.

The heat conduction in the moving body 7 is sufficient because of thepresence of the heat-conducting member 17 joined to the moving-bodycontact spring portion 4 and the moving-body main ring portion 6,despite the presence of the moving-body unwanted-oscillation damper 5having low heat conductivity.

Because of its flexibility, the heat-conducting member 17 does not limitthe relative positions of the moving-body contact spring portion 4 andthe moving-body main ring portion 6. Thus, the function of themoving-body unwanted-oscillation damper 5 can be maintained.

Furthermore, although the oscillation-propagation blocking damper 8 haslow heat conductivity too, the heat conduction between the moving-bodymain ring portion 6 and the disc spring 9 is sufficient because theheat-conducting member 18 is joined to the moving-body main ring portion6 and the disc spring 9.

Because of its flexibility, the heat-conducting member 18 does not limitthe relative positions of the moving-body main ring portion 6 and thedisc spring 9. Thus, the function of the oscillation-propagationblocking damper 8 can be maintained.

In addition, the heat conduction between the disc spring 9 and theoutput shaft 11, which are fastened to each other, is performed not onlythrough the fastening surfaces with respect to the disc-spring fixingmember 10 having thermal contact resistance, but also through theheat-conducting member 19 joined to the disc spring 9 and the outputshaft 11.

The heat conduction through these heat-conducting members 17 to 19prevents temperature rise of the oscillator 3 and moving body 7, as wellas degradation of the motor performance due to the temperature rise.

Furthermore, because the function of the moving-bodyunwanted-oscillation damper 5 and oscillation-propagation blockingdamper 8 is not degraded, excellent motor performance can be achieved.

As has been described above, by providing the dampers, which constitutethe oscillatory wave motor, and the flexible heat-conducting members,which form the heat-conducting paths in addition to the heat conductionby the oscillator supporting member, the heat can be dissipated withoutinhibiting the oscillation of the oscillator and the function of thedampers and pressure member.

Accordingly, the heat dissipation can be facilitated without affectingthe motor performance, thereby preventing temperature rise of the motorand achieving excellent motor characteristics.

Furthermore, by forming the heat-conducting members from string-like orthin plate-like flexible heat-conducting members that are different fromthe fastening members, heat can be dissipated without inhibiting theoscillation of the oscillator.

Accordingly, the heat dissipation can be facilitated without affectingthe motor performance, thereby preventing temperature rise of the motorand achieving excellent motor characteristics.

Note that the present invention can be applied to a damper, anoscillator supporting portion, and a fastening portion betweencomponents of an oscillatory wave motor having a configuration differentfrom above.

Second Embodiment

Referring to FIG. 2, an example of the configuration of an oscillatorywave motor according to a second embodiment of the present inventionwill be described.

The oscillatory wave motor according to this embodiment has a damperdifferent from that of the oscillatory wave motor according to the firstembodiment.

That is, in the oscillatory wave motor according to this embodiment, adamper for attenuating unwanted vibrations of the oscillator is providedbetween the oscillator and a member constituting the oscillatory wavemotor, other than the oscillator.

In FIG. 2, components denoted by the same reference numerals as in FIG.1 are the same components as in the first embodiment. Thus, detaileddescriptions thereof will be omitted, and portions different from thefirst embodiment will be described.

An oscillator unwanted-oscillation damper 21 that attenuates unwantedvibrations of the oscillator is provided between the base 14 and thepiezoelectric element 1 constituting the oscillator 3.

This serves to attenuate unwanted vibrations of the oscillator causingsqueal noise, which is different from driving vibration.

A heat-conducting member 22 similar to the one according to the firstembodiment, which is joined to the oscillator 3 and the base 14,conducts the heat of the oscillator 3 to the base 14 to dissipate theheat, without affecting the driving vibration of the oscillator 3 andthe function of the oscillator unwanted-oscillation damper 21.

Third Embodiment

Referring to FIG. 3, an example of the configuration of an oscillatorywave motor according to a third embodiment of the present invention willbe described.

In this embodiment, similarly to the first embodiment, a heat-conductingpath is formed by a heat-conducting member, in addition to the heatconduction by the pressure member.

Among the members constituting the oscillatory wave motor, not only thedampers, which are made of rubber or the like, but also pressuremembers, such as pressure springs, which bring the oscillator intofrictional contact with the moving body, prevent heat conduction.

The reason is as follows. That is, the pressure spring needs to have asmall spring constant so that the pressure can be precisely set andvariations in performance, due to a change in pressure, can beprevented, even if abrasion of the frictional driving surfaceprogresses.

As a result, the thickness, if it is a plate spring, or the diameter, ifit is a coil spring, is reduced as much as possible. Because thisreduces the cross-sectional area of the heat-conducting path of thepressure member, the pressure members, such as the pressure springs,inhibit heat conduction.

In FIG. 3, components denoted by the same reference numerals as in FIG.1 are the same components as in the first embodiment. Thus, detaileddescriptions thereof will be omitted, and portions different from thefirst embodiment will be described.

FIG. 3 shows a heat-conducting member 23 similar to the one according tothe first embodiment, which is joined to a moving-body contact springportion 4′ and the output shaft 11. The heat generated at the outsidediameter portion 3-b of the oscillator 3 and the heat generated at thefrictional driving surface between the oscillator 3 and the moving body7 are conducted to the output shaft 11 through the moving-body contactspring portion 4′.

The moving-body contact spring portion 4′ has a smaller inner diameterthan the moving-body contact spring portion 4 according to the firstembodiment, so that the length of the heat-conducting path provided bythe heat-conducting member is reduced to increase the heat conductivity.

When the heat-conducting member 23 is not provided, heat is conductedthrough the moving-body unwanted-oscillation damper 5, theoscillation-propagation blocking damper 8, and the disc spring 9,serving as the pressure member, which have low heat conductivity.Therefore, temperature rise of the motor and degradation of the motorperformance due to the temperature rise occur. However, temperature riseof the motor and degradation of the motor performance due to thetemperature rise can be prevented by heat dissipation utilizing heatconduction through the heat-conducting member 23.

Because the heat-conducting member 23 is flexible, the disc spring 9 isnot deformed.

In the oscillatory wave motors according to the embodiments of thepresent invention, the heat-conducting members are disposed in additionto the heat-conducting path that conducts heat generated by theoscillatory wave motor through the oscillator supporting member thatsupports the oscillator, or the heat-conducting path that conducts heatthrough the moving body.

Accordingly, the heat dissipation can be facilitated without inhibitingthe function of the pressure member, i.e., without affecting the motorperformance, thereby preventing temperature rise of the motor andachieving excellent motor characteristics.

Although the pressure member according to this embodiment is composed ofa disc spring, it is not limited thereto and may be a coil spring or aplate spring of another shape.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-065635 filed Mar. 23, 2010, which is hereby incorporated byreference herein in its entirety.

1. An oscillatory wave motor comprising: an oscillator including anoscillation body and an electro-mechanical energy-converting element;and a flexible heat-conducting member configured to dissipate heatgenerated by the oscillatory wave motor, wherein the oscillatory wavemotor drives a moving body in contact with a contact portion formed inthe oscillation body by an elliptical movement of the oscillator, andwherein the heat-conducting member is provided in addition to aheat-conducting path that conducts heat generated by the oscillatorywave motor through an oscillator supporting member that supports theoscillator or a heat-conducting path that conducts heat through themoving body.
 2. The oscillatory wave motor according to claim 1, whereina pressure member applies pressure to the moving body with a damper,which blocks propagation of the oscillation of the moving body,therebetween, and wherein the moving body and the pressure member arejoined by the heat-conducting member.
 3. The oscillatory wave motoraccording to claim 1, wherein the moving body includes a moving-bodymain ring portion, a moving-body contact spring portion, and a damperprovided therebetween to attenuate unwanted vibrations of the movingbody, and wherein the moving-body main ring portion and the moving-bodycontact spring portion are joined by the heat-conducting member.
 4. Theoscillatory wave motor according to claim 1, wherein the oscillatorincludes a damper provided between the oscillator and another componentof the oscillatory wave motor to attenuate unwanted vibrations of theoscillator, and wherein the oscillator and the other component of theoscillatory wave motor are joined by the heat-conducting member.
 5. Theoscillatory wave motor according to claim 1, wherein the heat-conductingmember has a string-like shape.
 6. The oscillatory wave motor accordingto claim 1, wherein the heat-conducting member has a thin plate-likeshape.
 7. The oscillatory wave motor according to claim 1, wherein theheat-conducting member is made of a material containing at least one ofmetal, graphite, and carbon fiber.